Reflector



June 3, 1930. I HUNT 1,761,919

REFLECTOR Filed Sept. 1, 1927 Patented June 3, 1930 UNITED STATES PATENT OFFICE JOHN H. H UNT, 011 DETROIT, MICHIGAN, ASSIGN OR TO GENERAL MOTORS RESEARCH CORPORATION, 013 DETROIT, MICHIGAN, A CORPORATION OF DELAWARE REFLECTOR Applicationfiled September 1, 1927. Serial No. 216,901.

This invention relates to reflectors and more particularly to a reflector for use in a headlight of an automotive vehicle.

The broad objects of the invention are to provide a reflector which will produce the desired light pattern and which is capable of being reproduced accurately and easily, simply by a statement of dimensions.

It is an object of this invention to combine a paraboloidal or hyperboloidal surface with an ellipsoidal surface to produce a reflector of the type desired. In order to adapt a paraboloidal or hyperboloidal reflector for use with a two filament bulb, the

upper part of the reflector must be modified to cast the light generally downward so that the top of the beam will be responsive to a change from one filament to the other. 'With the upper part of the reflector elliptic,

V the light will be cast downward as desired,

the source of light being at the focus. There are several objects in view in com- :bining the surfaces referred to. One ad- Vantage is that is provides a deeper light, that is, a greater vertical depth of beam without'shifting the position of maximum candle power in the beam. A further important feature of my invention resides in the fact that one reflector may have several 0"zones which may be hyperboloidal, paraboloidal or ellipsoidal, and with the focal length the same and the source of light at v or near the focus, the beam or pattern produced by a reflector of any given dimensions 'i can be fairly closely calculated. In other words, it is not a hit and miss proposition, as the problem is simplified by the fact that 'oneof the factors, that is, the focal length, is a' constant. This enables the designer to 40 secure a pattern of the desired shape and intensity by varying the eccentricity of the I hyperboloidal or ellipsoidal'surfaces.

Since the problem is one of combining an ellipsoidal surface with a surface which may be either paraboloidal or hyperboloidal but which may not be ellipsoidal, I have used the term open figure to include a parabola or hyperbola, but not to include an ellipse. Other objects of the invention will appear 5 in the course of the following description,

taken in connection with the accompanying drawing and appended claims.

In the drawing:

Figure l is a front view of the punch for forming by improved reflector.

Figure 2 is a side elevation of the punch.

Figure 3 is a horizontal section through the center of the punch after it has been striped or zoned.

Figure 4 is a front view of a reflector formed with my improved punch.

Figure 5 is asection on the line 5 5 of Figure 4;" I

The form of my'improved reflector is best understood by a description of the method of making the punch. The first operation consists in turning a surface of revolution on a blank. The surface may be a paraboloid or it may be hyperboloid with a fairly low eccentricity. While a parabolic reflector with the light at the focus may be theoretically the most desirable, still the light source is never the theoretical point and for this reason, I do not wish to be limited to a particular geometric surface of revolution. The surface of revolution is theoretically generated by revolution of the curve indicated by the dotted line 1 in Figure 2 and the axis of revolution is denoted by reference character 10. The lower part of the punch marked 11 is thus produced and remains unchanged, the modificationsbeing made in the upper part of the punch. 1 c A The neXt operation resides in modifying the upper part of the reflector by means of an elliptic curve. This is done by taking an" ellipse "of the same focal length as the original parabola or hyperbola andfsuperimposing it thercon, The foci and'vertices of the two curves then coincide while the top of'the 'figureis dropped the distance between the points 4 and 5. The ellipse is then rotated about axis 20 parallel with but spaced belowthe' axis 10 the distance between'the points 4 and 5;

This method produces a surface 22 above the line 12 whose radial sectionsare elliptical with foci falling on a semicircle whose radius is equal to thedistancethe axis of within the limits of the original parabolbid.

If the ellipse is of sufficiently low eccentricity, this third zone will not be necessary;

lVith the punch in this condition a plain reflector can be produced for use with a vertically fluted lens. I have illustrated my invention, however, as applied to a fluted reflector. Figure 3 illustrates the arrange ment of the vertical flutes 7 on the punch. The reflector formed from this punch is shown in Figures 4 and 5, As illustrated in these figures and in Figure 2, there are three zones to the reflector. Disregarding the flutes the lower zone 11, beneath. the lines 12, is part "of. the original surface of v a surface generated by the rotation of an open curve of a come section about its axis, and

the upper portion of which is a converging focalizing surface generated by the rotation of a curve of come sectlon of less eccentricity than the first named curve about an axis 7 parallel to andbelow the axis of the former and so offset therefrom that the generated 7 surfaces will intersect in curved lines above ahorizontal plane passing through the axis of generation Of the lower surface; the generating curve of the upper portion of the reflector when inthe vertical plane having its focus and vertex coincident substantially with the focus and vertex of the generating curve of the lower portion of the reflector.

' Intestimony whereof I affix'my-signature. 1'

JOHN H. HUNT.

revolution and is hyperboloidal or, paraboloidal as described in detail above. The second .zone 22, above line 12 and below line 23, is elliptic as described above. The

third zone 33, which is above. the line 23,; I

may be a surface of any shape which throws I the light still; lowerthan the second zone. The vertical flutes 7 merely effect a lateral spreading of the beam and, as indicated' above, this is not an essential feature of my invention as the lateral spread can be secured by leaving the surface of the reflector plain and using a vertically fluted lens.

It is to be understood that the terms above, below, top, and bottom asused inthis application are relative terms only. If the headlamp is used for some,v

other purpose than road lighting, or if State requirements. as to light distribution are changed, it may obviously be desirable to turn or tilt the lamp inone direction, or

the other. Suchchanges would not, how'- ever, affect the relative location of the parts of the reflector with respect to eachother and consequently would not take. the cone struction outside of the scope of the append ed claims.

I claim:

1. A reflector comprising a substantially paraboloidal lower portion, an, intermediate portion joining the lower portion without,

abrupt break in curvature,said intermediate.

portion being formed bythe rotation of an. ellipse about an axis displaced below the.

axis of the lower portion, and an upperportion bent downwardly with respect to said lower and immediate portions.

2. A reflector the lower portion of which is, 

